Machine type communication (MTC) refers to a communication scheme between one or more machines and is also referred to as machine-to-machine (M2M) communication. Here, a machine refers to an entity which does not require direct human operation or intervention. For example, the machine may include not only a device including a mobile communication module, such as a meter or a vending machine, but also a user equipment such as a smartphone which is capable of automatically accessing a network without operation/intervention of a user to perform communication. Various examples of such a machine are referred to as an MTC device or terminal in the present specification. That is, MTC refers to communication performed by one or more machines (that is, MTC devices) without human operation/intervention.
MTC may include communication between MTC devices (e.g. device-to-device (D2D) communication) and communication between an MTC device and an MTC application server. Examples of communication between an MTC device and an MTC application server include communication between a vending machine and a server, communication between a point of sale (POS) device, and communication between an electric meter, a gas meter, or a water meter and a server. MTC-based applications may include security, transportation, healthcare, etc.
Meanwhile, when congestion or overload occurs in a network, congestion control may be performed in a control plane. For example, network congestion control may be performed in a non-access stratum (NAS) level which is the uppermost stratum in the control plane between a terminal and a network control node in a radio interface.
Generally, when a network congestion state occurs, the network may configure a back-off timer for inhibiting a request for the network for a predetermined time. According to operation of a currently defined wireless communication system, when the terminal moves to an unregistered area while the back-off timer is running in the terminal, the terminal cannot perform area update for the network due to restrictions caused by the back-off timer. In this case, even though the network transmits a paging message in order to search for the terminal, the terminal cannot receive the paging message and thus cannot perform paging response operation. The terminal cannot be offered an important mobile terminated (MT) service (e.g. MT-call/short message service (SMS), etc.) due to failure of such a paging procedure. Thus, operation related to network congestion control, performed between the terminal and the network, is not clear and a service cannot be correctly provided to the terminal. Especially, in a wireless communication system supporting MTC, since the network should provide services to lots of terminals (or MTC devices), the afore-described network congestion situation needs to be clearly processed.